The present invention relates to an ultrasound diagnostic apparatus, particularly to an ultrasound diagnostic apparatus which transmits an ultrasonic beam from an ultrasound probe toward a subject, receives ultrasonic echoes reflected by the subject by an ultrasound probe and sends that reception signal to an apparatus body, wherein the apparatus body and ultrasound probe are connected by a connection cable.
In recent years, ultrasound diagnostic apparatus that use ultrasound images have been put to use in the medical field. In general, this type of ultrasound diagnostic apparatus has an ultrasound probe equipped with a plurality of ultrasound transducers arranged in an array, and an apparatus body connected to the ultrasound probe via a connection cable. It transmits ultrasonic waves from the ultrasound probe toward a subject, receives the ultrasonic echoes from the subject by the ultrasound probe, and generates an ultrasound image by digitally processing the reception signals in the apparatus body.
Here, in the connection cable which connects the ultrasound probe and the apparatus body, the reception signals obtained by the ultrasound transducers of the ultrasound probe are sent from the ultrasound probe to the apparatus body, and additionally, drive signals for driving the ultrasound transducers are sent from the apparatus body to the ultrasound probe. For this reason, transmission signal wires for sending the drive signals and reception signal wires for sending the reception signals corresponding to the plurality of ultrasound transducers arranged in the ultrasound probe are required, and as the number of ultrasound transducers increases, the number of signal wires in the connection cable also increases.
When the number of signal wires increases, problems occur in that the connection cable becomes thick and heavy, and maneuverability of the ultrasound probe decreases.
If each signal wire of the connection cable is made lighter and narrower in order to counteract these problems, it causes problems in that mixing in of external noise and attenuation due to the resistance of the signal wires occur, and detection precision of the reception signal is markedly reduced.
Thus, in JP 2005-279130 A, for example, a technique was proposed wherein the drive signals and the reception signals for the ultrasound transducers are sent by few signal wires, regardless of the number of ultrasound transducers, by connecting a delay circuit to each of the plurality of ultrasound transducers in the ultrasound probe and sending signals that are divided over time corresponding to the plurality of ultrasound transducers.
Also, in JP 2007-209700 A, an apparatus was proposed wherein the number of signal wires of the connection cable is reduced by actively switching between transmission of the drive signals and reception of the reception signals via a switch, and detection precision of the reception signals is improved by incorporating a preamp in the ultrasound probe and amplifying the reception signals.
However, in the ultrasound diagnostic apparatus according to JP 2005-279130 A, a certain delay is provided to both the high-voltage drive signals for driving the ultrasound transducers and to the tiny reception signals, but in general, the time precision of analog delay wires is low, and it is difficult to delay drive signals which are more than 100 V at maximum with high precision.
Also, realizing the apparatus disclosed in JP 2007-209700 A is difficult because a practical electronic switch that can operate at a high speed of about 1 μs while having a breakdown voltage of 100 V or above has not yet been developed.